1. Field of the Invention
The invention generally relates to a circuit substrate structure, and more particularly, to a circuit substrate structure with an active surface having a metallic plating layer. The structure of the invention are suitable for a semiconductor substrate with miniaturized electronic devices already made and a semiconductor substrate without other miniaturized electronic devices and meanwhile can be further applicable in fabricating a reflective layer disposed on a ceramic substrate with a circuit and a metallic substrate with a circuit.
2. Description of Related Art
Along with the progress of semiconductor technology, a light-emitting diode (LED) has larger and larger power, and the intensity of the emitted light thereof becomes higher and higher. In addition, LEDs have advantages, such as power-saving, long lifetime, environment-friendly, fast starting, small size and so on, so that LEDs are widely applied in illumination equipment, traffic sign light, display, optical mouse and the like and would gradually substitute traditional fluorescent lamps.
In an LED package structure, there are an LED unit and a control unit, in which the control unit has pads thereon for electrically connecting the LEDs. In order to effectively reflect the light emitted from the LED unit to advance light-emitting efficiency, a reflective layer can be employed and disposed in the LED package structure, so that the light emitted from the LED unit can be effectively reflected by the reflective layer to advance light-emitting efficiency.
For example, a reflective layer made of silver (Ag) has the best effect, in which the control unit can be coated with silver thereon by plating, evaporation or vacuum sputtering. Plating silver is not a standard semiconductor process and has a practical difficulty when mass producing semiconductor substrates, while when making evaporation or vacuum sputtering to plate a reflective layer on the control unit, each pad may contact the reflective layer to electrically connect each other to result in an unexpected electrical connection, which would affect the normal operation of the LED unit. As a result, when a semiconductor device and a reflective layer are integrated into a single chip, how to avoid the reflective layer plated on a control unit and fabricated by evaporation or vacuum sputtering to contact pads becomes an important project in fabricating an LED package structure.